Parts of a Sprinkler Valve – Solenoid, Diaphragm, Bonnet

All 13 parts on the diagram

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On the outside 6

Solenoid wires Two wires that carry power from the timer.
Flow control Turned to limit how much water the valve lets through.
Solenoid An electric coil; powered by the timer, it lifts the plunger.
Bleed screw Loosened by hand, it opens the valve without the timer.
Bonnet The cover on top; it comes off to reach the diaphragm.
Flow arrow It shows which way the water flows through the valve.

Inside the valve 7

Plunger A small pin; lifted, it lets water out from above the diaphragm.
Spring (diaphragm spring) It pushes the diaphragm down toward the seat.
Diaphragm A rubber disc that lifts off the seat to open the valve.
Valve seat The rim the diaphragm closes against.
Inlet Water from the supply waits here under pressure.
Valve body The main shell that the pipes screw into.
Outlet Water leaves here for the sprinklers.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it. Wikipedia, Solenoid valve and Irrigation sprinkler (https://en.wikipedia.org/wiki/Solenoid_valve, https://en.wikipedia.org/wiki/Irrigation_sprinkler); one irrigation maker's valve installation sheets (https://archive.org/details/manuals-plus-rain-bird-cp-cpf-series-valve-installation-and-operation-m-47c8251f, https://archive.org/details/manuallib-id-2723412, one company, one source); a second maker's valve guides and its diaphragm replacement sheet (https://archive.org/details/manualzilla-id-6964531, https://archive.org/details/manualzilla-id-6964529, https://archive.org/details/manualzilla-id-6964386, one company, one source); a third maker's valve system manual (https://archive.org/details/manualzilla-id-6339336). The makers' documents were read as archive.org full text for their part names only. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; a schematic of no maker's product, nothing traced. Licence: own work

How it works

A sprinkler valve turns one zone of a lawn system on and off when the timer sends power to its solenoid. The first drawing shows the valve from the side. The second cuts it through, open, with water passing under the lifted diaphragm.

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On the outside

The body joins the pipe, and its flow arrow shows the way the water runs. The bonnet covers the top. On it stand the solenoid with its two wires, the flow control and the bleed screw.

How it opens

Closed, the spring and the water above the diaphragm hold it down on the valve seat. When the timer powers the solenoid, the plunger lifts and lets that water escape. The pressure in the inlet then lifts the diaphragm, and water runs to the outlet.

Questions and answers

What are the parts of a sprinkler valve?

A body with an inlet and an outlet, a bonnet on top, a diaphragm and spring inside, a valve seat, and a solenoid with a plunger and two wires. Many also have a flow control and a bleed screw.

What does the solenoid do on a sprinkler valve?

It is an electric coil on top of the valve. When the timer sends it power it becomes a magnet and lifts a small plunger, which lets water out from above the diaphragm so the valve opens.

What is the bleed screw on a sprinkler valve for?

It opens the valve by hand. Loosening it lets water out from above the diaphragm, the same job the solenoid does, so the zone runs without the timer.

What does the diaphragm do?

It is the rubber disc that opens and closes the valve. Water pressure above it holds it down on the seat. When that water is let out, the pressure below lifts it and water flows through.